The present invention refers to a lifting apparatus for swiveling parts of a piece of furniture, and in particular to a lifting apparatus of the type having a scissor jack and an electromotive drive unit essentially including a threaded spindle and a gear motor.
German publication DE-GM 91 03 817 describes a lifting apparatus of this type having a d.c. gear motor with an output link in form of a rotatably driven screw nut with female threaded to allow the d.c. gear motor to shift along a stationary threaded spindle. Depending on the direction of movement of the d.c. gear motor, the scissor jack with its scissors-type members collapses or moves apart. Even though this lifting apparatus has proven reliable, practice has shown that the scissor jack has the tendency to selfcontract over a portion of the lift, thus creating a danger of injury or damage. This danger is however not only caused by the scissor jack but may also be triggered by the furniture part being swiveled, e.g. the foot part or the head part of a slatted base. In addition, this lifting apparatus has the drawback that the scissor jack or the furniture part being swiveled suddenly drops once the obstruction has been removed.